vitamin

vitamin

[vi´tah-min]

an organic substance found in foods and essential in small quantities for growth, health, and the preservation of life itself. The body needs vitamins just as it requires other food constituents such as proteins, fats, carbohydrates, minerals, and water. The absence of one or more vitamins from the diet, or poor absorption of vitamins, can cause deficiency diseases such as rickets, scurvy, and beriberi. Vitamins serve as coenzymes or cofactors in enzymatic reactions. They are required only in trace quantities because they are not consumed in the reactions. The major vitamins are designated by the letters A, C, D, E, and K, and the term B complex. The B vitamins and vitamin C are water soluble. The rest are fat soluble and are not absorbed unless the body's digestion and absorption of fats is normal. Deficiencies of the fat-soluble vitamins can be produced by various malabsorption syndromes.

Vitamin A. Vitamin A helps to maintain epithelial tissues which cover the body and line certain internal organs. This vitamin also is essential for the proper growth of skeletal and soft tissues, and is necessary for light-sensitive pigments in the eye that make night vision possible. The particular manifestation of vitamin A deficiency depends upon the age of the patient. Among the most common symptoms of vitamin A deficiency is night blindness. The skin may also be affected, becoming dry and pimply like a toad's skin.

Vitamin A occurs in nature in two forms: retinol (vitamin A1) and dehydroretinol (vitamin A2). It is manufactured by animals and humans from carotenes found in green leafy and yellow vegetables, including kale, broccoli, spinach, carrots, squash, and sweet potatoes. It is obtained directly by eating animal products such as liver, eggs, whole milk, cream, and cheese. A toxic syndrome (hypervitaminosis A) can result from excessive vitamin intake. It is marked by generalized pruritus, desquamation of the skin, loss of hair, and hyperostoses.

The B Complex. The original “vitamin B” was found to be a group of vitamins, each differing chemically and each individually important in the body. For convenience, these vitamins are referred to as one group since they are often found together in foods. Deficiency in only one of these vitamins is rare, and the deficiency disease attributed to lack of one vitamin B usually is complicated by deficiencies of the others as well.

Vitamin B1 (Thiamine). This vitamin is necessary to break down and release energy from carbohydrates. Lack of thiamine can cause loss of appetite, certain types of neuritis, and, in severe cases, beriberi, which affects the brain, heart, and nerves. The best sources of thiamine are yeasts, ham and certain pork cuts, liver, peanuts, whole-grain and fortified cereals and breads, and milk. The vitamin is easily destroyed by cooking and may also be lost by dissolving in the cooking water. Because the body does not store thiamine well, foods that are good sources of it should be included in each day's diet.

Vitamin B2 (Riboflavin). This vitamin functions as a coenzyme concerned with oxidative processes. Riboflavin deficiency (ariboflavinosis) was at one time a common vitamin deficiency disease in the United States. It still occurs in parts of Asia, the West Indies, and elsewhere. Symptoms include open sores at the corners of the mouth and on the lips, a purple-red, inflamed tongue, seborrheic dermatitis, and corneal and other eye changes. The main food sources of riboflavin are milk, liver, kidney, heart, green vegetables, dried yeasts, and enriched breads and cereals. It is not usually affected by cooking, but is destroyed by light.

Niacin (Nicotinic Acid). This B vitamin appears to act in enzyme systems to utilize carbohydrates, fats, and amino acids. Niacin deficiency causes pellagra, once a major deficiency disease in the United States. Symptoms of pellagra involve the skin and digestive and nervous systems. Niacin also has vasodilating activity. Food sources of niacin are various high-protein foods such as liver, yeast, bran, peanuts, lean meats, fish, and poultry.

Vitamin B12 (Cyanocobalamin). This vitamin contains cobalt and is needed for the efficient production of blood cells and for the health of the nervous system. Only small amounts of B12 are required by the body. The activity of this vitamin is associated with that of another B vitamin, folic acid. Inability to absorb vitamin B12 occurs in pernicious anemia, in which a substance normally secreted by the stomach, called intrinsic factor, is missing. Intrinsic factor is needed to absorb vitamin B12 in the small intestine. Injections of vitamin B12 can control pernicious anemia. Poor absorption of vitamin B12 also occurs in sprue.

Vitamin B12 is not found in plant foods. The main sources in the human diet are animal products such as milk, eggs, and liver. Probably the ultimate source of B12 is bacterial production in animal intestines. This production occurs in humans, and in normal persons probably meets some or perhaps all of the body's requirements.

Other Members of the B Vitamin Complex. These include vitamin B6 (pyridoxine), biotin, folic acid, pantothenic acid, choline, inositol, and p-aminobenzoic acid. Vitamin B6 deficiency can cause convulsions, lethargy, mental changes and retardation, inflammation of the skin, and anemia. These substances, like most other members of the B complex, are widely found in fruits, vegetables, meat, and whole-grain cereals.

Vitamin C (Ascorbic Acid). This vitamin is necessary for the health of supporting tissues such as bone, cartilage, and connective tissue. Deficiency produces scurvy. Vitamin C is found in fresh fruits and vegetables, including citrus fruits, tomatoes, brussels sprouts, and to some extent whole potatoes. Cooking and storage destroy much of the vitamin C content of foods.

Vitamin D. The action of sunlight on the skin changes certain substances in the body into vitamin D, a term for any of several active substances required for the utilization of calcium and phosphorus, which are essential for the growth and maintenance of bone. These include cholecalciferol and ergocalciferol (known collectively as calciferol). Vitamin D deficiency causes rickets in children and osteomalacia and osteoporosis in adults. Rickets is usually caused either by a diet deficient in vitamin D or by insufficient exposure to sunlight. Few foods contain vitamin D. The only rich natural sources are fish liver oil and the livers of animals feeding on fish. For this reason vitamin D often is added to milk. A toxic syndrome (hypervitaminosis D) can result from excessive vitamin D intake. It results in hypercalcemia with its typical symptoms of weakness, fatigue, loss of weight, and impairment of renal function.

Vitamin E. There are at least eight different antioxidants in this group, of which alphatocopherol is the most common; they prevent the oxidation of unsaturated fatty acids, thus preventing cell damage that can lead to neurological symptoms. Because of its ubiquitous nature, supplemental intake of vitamin E is not necessary. It is found in wheat germ oil, cereals, egg yolk, and beef liver.

Vitamin K. Any of a group of vitamins including vitamin K1 (phytonadione) and vitamin K2 (menaquinone) found in alfalfa, spinach, cabbage, putrefied fish meal, and hempseed, which promote blood clotting by increasing the synthesis of prothrombin by the liver; therefore, deficiency of vitamin K delays clotting. Symptoms of vitamin K deficiency are excessive bleeding and bruises under the skin. Generally, the bacteria of the intestine produce vitamin K in quantities that are adequate (provided it can be absorbed), except in newborn infants, in whom the deficiency is most frequently found.

Vitamin Supplements. The exact vitamin requirements for good health often are not known with accuracy; they vary with age, weight, sex, and state of health. The need for certain vitamins increases with fever, some diseases, heavy exercise, pregnancy, and nursing. Persons eating an adequate, varied diet of meats, fruits and vegetables, and dairy products will receive enough vitamins to meet normal requirements. Public health measures such as the addition of vitamin D to milk and the B vitamins to bread and other cereal products have helped to combat deficiency diseases.

The use of vitamin supplements is expensive and in general unnecessary. Specialists in nutrition advise against taking supplementary vitamins unless they are prescribed for a specific reason. Overdoses of vitamins D, A, or K may result in serious disease, with the excess vitamins acting like poisons. Vitamins are commonly prescribed in infancy and childhood, during pregnancy and nursing, for elderly patients whose dietary habits are poor, and in clearly diagnosed deficiency states. These include not only the more familiar deficiency diseases already described but also alcoholism and chronic wasting diseases.

vi·ta·min

(vī'tă-min),

One of a group of organic substances, present in minute amounts in natural foodstuffs, that are essential to normal metabolism; insufficient amounts in the diet may cause deficiency diseases.

[L. vita, life, + amine]

vitamin

/vi·ta·min/ (vi´tah-min) any of a group of unrelated organic substances occurring in many foods in small amounts and necessary in trace amounts for the normal metabolic functioning of the body; they may be water- or fat-soluble.

vitamin A retinol or any of several fat-soluble compounds with similar biological activity; the vitamin acts in numerous capacities, particularly in the functioning of the retina, the growth and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Deficiency causes skin disorders, increased susceptibility to infection, nyctalopia, xerophthalmia and other eye disorders, anorexia, and sterility. As vitamin A it is mostly found in liver, egg yolks, and the fat component of dairy products; its other major dietary source is the provitamin A carotenoids of plants. It is toxic when taken in excess; see hypervitaminosis A.

vitamin B6 any of a group of water-soluble substances (including pyridoxine, pyridoxal, and pyridoxamine) found in most foods, especially meats, liver, vegetables, whole grains, cereals, and egg yolk, and concerned in the metabolism of amino acids, in the degradation of tryptophan, and in the metabolism of glycogen.

vitamin B12 cyanocobalamin by chemical definition, but generally any substituted cobalamin derivative with similar biological activity; it is a water-soluble hematopoietic vitamin occurring in meats and animal products. It is necessary for the growth and replication of all body cells and the functioning of the nervous system, and deficiency causes pernicious anemia and other forms of megaloblastic anemia, and neurologic lesions.

vitamin D either of two fat-soluble compounds with antirachitic activity or both collectively: cholecalciferol, which is synthesized in the skin and is considered a hormone, and ergocalciferol, which is the form generally used as a dietary supplement. Dietary sources include some fish liver oils, egg yolks, and fortified dairy products. Deficiency can result in rickets in children and osteomalacia in adults, while excessive ingestion can cause hypercalcemia, mobilization of calcium from bone, and renal dysfunction.

vitamin E any of a group of at least eight related fat-soluble compounds with similar biological antioxidant activity, particularly α-tocopherol but also including other isomers of tocopherol and the related compound tocotrienol. It is found in wheat germ oil, cereal germs, liver, egg yolk, green plants, milk fat, and vegetable oils and is also prepared synthetically. In various species it is important for normal reproduction, muscle development, and resistance of erythrocytes to hemolysis.

fat-soluble vitamins those (vitamins A, D, E, and K) that are soluble in fat solvents and are absorbed along with dietary fats; they are not normally excreted in the urine and tend to be stored in the body in moderate amounts.

vitamin K any of a group of structurally similar fat-soluble compounds that promote blood clotting. Two forms, phytonadione and menaquinone, exist naturally, and there is one synthetic provitamin form, menadione. The best sources are leafy green vegetables, butter, cheese, and egg yolk. Deficiency, usually seen only in neonates, in disorders of absorption, or during antibiotic therapy, is characterized by hemorrhage.

water-soluble vitamins the vitamins soluble in water (i.e., all but vitamins A, D, E, and K); they are excreted in the urine and are not stored in the body in appreciable quantities.

vitamin

(vī′tə-mĭn)

n.

1. Any of various fat-soluble or water-soluble organic substances that are essential in minute amounts for normal growth and activity of living organisms. They are synthesized by bacteria and plants and are obtained by animals chiefly in their diet.

2. A preparation containing one or more vitamins, often taken as a dietary supplement.

vi′ta·min′ic adj.

vitamin

[vī′təmin]

Etymology: L, vita + amine, ammonia

an organic compound essential in small quantities for normal physiological and metabolic functioning of the body. With few exceptions, vitamins cannot be synthesized by the body and must be obtained from the diet or dietary supplements. No one food contains all the vitamins. Vitamin deficiency diseases produce specific symptoms, usually alleviated by the administration of the appropriate vitamin. Vitamins are classified according to their fat or water solubility, their physiological effects, or their chemical structures. They are designated by alphabetic letters and chemical or other specific names. The fat-soluble vitamins are A, D, E, and K. The B complex and C vitamins are water soluble. See also avitaminosis, hypervitaminosis, oleovitamin, provitamin, and the specific vitamins.

vitamin

An organic nutrient required in small amounts by an organism, which it cannot synthesise and must obtain from external sources.

vitamin

Any of a number of organic accessory factors present in food–in addition to the basic components of carbohydrates, fats, proteins, minerals, water and fiber–which are necessary in minimal or trace amounts, often acting as coenzymes–daily requirements of individual vitamins are measured in mg to µg quantities, as the body either does not produce them or does so in minute quantities; water-soluble vitamins–B1, B2, B6, B12, C, are reasonably well-tolerated as they are easily excreted, while the lipid soluble–A, D, E, K vitamins accumulate in fat, have significant hepatotoxic potential. See Antioxidant vitamin, B complex vitamin, Multivitamin. Cf Chemoprevention, Pseudovitamin.

vi·ta·min

(vīt'ă-min)

One of a group of organic substances, present in minute amounts in natural foodstuffs, which are essential to normal metabolism; insufficient amounts in the diet may cause deficiency diseases.

[L. vita, life, + amine]

vitamin

an organic compound that is necessary in the diet for normal growth and health. Not all organisms require the same vitamins in their diet. For example, rats can synthesize vitamin C whereas humans cannot. Only small quantities are normally required in the diet, as vitamins usually act as COENZYMES or parts of coenzymes. They are divided into two types: fat-soluble (A, D, E and K) and water-soluble (B and C). See VITAMIN A, B-COMPLEX, ASCORBIC ACID, VITAMIN D, VITAMIN E, VITAMIN K.

vitamin,

vi·ta·min

One of a group of organic substances, present in minute amounts in natural foodstuffs, which are essential to normal metabolism; insufficient amounts in the diet may cause deficiency diseases.

[L. vita, life, + amine]

vitamin (vi´təmin),

n one of a number of unrelated organic substances that occur in small amounts in food and are required for normal metabolic activity. The vitamins may be water soluble or fat soluble.

vitamin A,

n (retinal, retinol, retinoic acid), a fat-soluble substance, occurring in several chemical forms in food and function: retinal, an aldehyde; retinol, an alcohol; and retinoic acid, an acid. All three function in calcified and epithelial tissue growth. The aldehyde-alcohol (retinal-retinol) interconversion allows regeneration of rhodopsin (visual purple) in the rod cells of the retina. A deficiency results in hyperkeratinization of nonsecretory protective epithelium, deranged secretory function of the mucous membrane, dark dysadaptation (night blindness), and possibly, enamel hypoplasia. Dietary sources include liver, kidney, and lung as well as carotenes (provitamins A) from the plant kingdom.

vitamin, ascorbic acid

n (vitamin C, antiscorbutic factor), a water-soluble vitamin resembling glucose in structure; it is found in citrus fruits, tomatoes, cabbage, and other fresh fruits and vegetables. Necessary for hydroxylation of peptide-bound lysine and proline to hydroxylysine and hydroxyproline during collagen synthesis. A deficiency leads to scurvy, in which pathologic signs are confined mainly to the connective tissues with hemorrhages, loosening of teeth, gingivitis, and poor wound healing.

n not truly a vitamin, because it can be synthesized in the body if sufficient precursors are available. Prevents the accumulation of fat in the liver of certain animal species. Occurs as a constituent of lecithin, sphingomyelin, and acetylcholine.

vitamin, cobalamin

n (antipernicious factor, vitamin B12, cyanocobalamin, erythrocyte maturing factor [EMF], extrinsic factor) a vitamin that contains cobalt and is essential for the maturation of erythrocytes. Inability of the body to produce intrinsic factor, which is necessary for vitamin B12 absorption, results in pernicious anemia. Liver, kidney, muscle, and milk are good sources.

n the group of lipid-soluble sterol compounds capable of preventing rickets. Of primary importance are D2, or ergosterol, from plants and D3, or cholecalciferol, from animal sources, especially fish liver oils. The latter is also formed in the skin from 7-dehydrocholesterol on exposure to ultraviolet light. Liver mitochondria further activate vitamin D to 25-(OH)-D, which in turn is metabolized to 1,25-(OH)2-D by the kidney. The dihydroxy metabolites significantly increase dietary calcium absorption and bone resorption to maintain proper blood calcium and phosphorus levels. A primary vitamin D deficiency results from inadequate exposure to sunlight and low dietary intake. Secondary deficiencies occur from abnormalities of intestinal resorption and interference with vitamin D hydroxylation. The manifestations of rickets include enamel hypoplasia, poorly calcified bones, bowed legs, and a deformed rib cage with beadlike swellings of the ribs (rachitic rosary) in infants and children and osteomalacia in adults. Vitamin D intake in excess is toxic.

vitamin E,

n (tocopherol, tocotrienol antisterility factor) the tocopherol and tocotrienols have varying degrees of vitamin E activity, but α-tocopherol is the most active. These fat-soluble compounds are found in eggs, muscle meats, liver, fish, chicken, oatmeal, and the oils of corn, soya, and cottonseed. In rats, the lack of vitamin E leads to fetus resorption in the female and atrophy of spermatogenic tissue with permanent sterility in the male. Vitamin E deficiency in humans is correlated with increased hemolysis of erythrocytes. The tocopherols prevent peroxidation of unsaturated fatty acids, and vitamin E requirements appear to be directly related to the dietary intake of unsaturated fatty acids. Although animals develop symptoms of muscular dystrophy on deficient diets, the vitamin has no effect on the human disease.

vitamin, ergocalciferol,

n See vitamin D.

vitamin, folacin,

n (adermine, folic acid, citrovorum factor, pteroylglutamic acid, vitamin M, vitamin Bc) occurs in many tissues as the free acid or is conjugated with one to seven glutamic acid molecules. Green, leafy vegetables; kidney; liver; and yeast are good sources, and bacterial synthesis in humans occurs readily. As a coenzyme, the vitamin serves as a carrier of one-carbon units (formyl, hydroxymethyl, formimino groups), especially in the synthesis of nucleoproteins. Inadequate folate levels produce a variety of species-dependent symptoms that include megaloblastic anemia in humans.

vitamin G,

n See vitamin, riboflavin.

vitamin H,

n See vitamin, biotin.

vitamin, inositol

n (myo-inositol, meso-inositol), a six-carbon alcohol closely related to the hexoses. Inositol is not truly a vitamin because the body can synthesize significant amounts from glucose. Its biologic role is not established, but it is essential to the growth of liver and bone marrow cells and helps alleviate fatty livers.

vitamin K,

n (phytonadione, antihemorrhagic factor), one of the many fat-soluble naphthoquinone compounds with vitamin D activity. Vitamin K1 is found primarily in leafy vegetables, K2 is synthesized by human intestinal bacteria, and K3 (menadione, N.F.) is a synthetic compound. Vitamin K is essential for the synthesis of prothrombin by the liver. A dietary deficiency of vitamin K is rare, however. The vitamin has been used in conjunction with extensive oral antibiotic therapy to treat hemorrhagic disease of the newborn, hemorrhage of obstructive jaundice, and sprue, and during anticoagulant therapy. Prothrombin, Stuart factor, Christmas factor, and serum prothrombin conversion accelerator require vitamin K for their synthesis.

vitamin, niacin

n (nicotinic acid, nicotinamide, niacinamide, pellagra-preventive factor), a deficiency of niacin or its amide derivative, niacinamide, results in acute pellagra that is characterized by dermatitis, diarrhea, dementia, stomatitis, and glossitis. Dietary sources include liver, kidney, lean meats, wheat germ, yeast, soybeans, and peanuts. There is some intestinal synthesis by bacteria. Although the amino acid tryptophan contributes to the body supply of niacin, sufficient vitamin B6 must be present for its metabolism. Niacin and niacinamide are interconvertible in the body, and the latter functions as a constituent of two coenzymes, NAD and NADP, which operate as hydrogen and electron transfer agents by virtue of their reversible oxidation and reduction in several enzyme systems.

vitamin, pantothenic acid

n (pantothen, panthenol), this vitamin is a component of coenzyme A and thereby functions in the metabolism of lipids, carbohydrates, and proteins. A deficiency is unusual because of its wide distribution, but a “burning feet syndrome” has been reported in people suffering from acute malnutrition.

vitamin, pyridoxine

n (vitamin B6, pyridoxal, pyridoxol, pyridoxamine) part of the B complex vitamins, the group includes three chemically related substances: pyridoxol, pyridoxal, and pyridoxamine, all of which serve as substrate in the formation of pyridoxal phosphate, the prosthetic group for several enzymes that decarboxylate, deaminate, transaminate, or desulfurate specific amino acids. It further functions in porphyrin, fatty acids, and cholesterol metabolism. Deficiency signs include an acrodynia-like syndrome, convulsive seizures, arteriosclerotic-like lesions, hypochromic microcytic anemia, and impaired antibody formation. Dietary sources include wheat; corn; liver; milk; eggs; and green, leafy vegetables.

vitamin, retinal,

n See vitamin A.

vitamin, retinoic acid,

n See vitamin A.

vitamin, retinol,

n See vitamin A.

vitamin, riboflavin

n (vitamin B2, vitamin G, lactoflavin) a heat-stable B complex vitamin that functions as a component of FAD and FMN for the reversible transfer of hydrogen and electrons in several enzyme systems. It is found in green, leafy vegetables; whole grains; eggs; liver; milk; and legumes; small amounts are synthesized in the intestinal tract by microorganisms. Signs of ariboflavinosis include angular stomatitis, seborrheic dermatitis of the face, and glossitis (magenta tongue).

vitamin, thiamine

n (vitamin B1, aneurine, antiberiberi factor, antineuritic factor) a B complex vitamin found primarily in plants, especially legumes; whole grains; and green, leafy vegetables; it is also synthesized by bacteria in the large intestine, which is not a reliable source. Thiamine pyrophosphate (TPP, cocarboxylase) is a coenzyme in the oxidative decarboxylation of pyruvate and α-ketoglutarate, in the transketolase reaction of glucose metabolism and in the metabolism of branched chained amino acids. A deficiency results in beriberi.

vitamin, tocopherol,

n See vitamin E.

vitamin, tocotrienol,

n See vitamin E.

vitamin

an organic substance found in foods and essential in small quantities for growth, health and survival. The body needs vitamins as well as other food constituents such as proteins, fats, carbohydrates, minerals and water. The absence of one or more vitamins from the diet, or poor absorption of vitamins, can cause deficiency diseases such as rickets, enzootic muscular dystrophy and polioencephalomalacia.

Vitamins serve as coenzymes or cofactors in enzymatic reactions. They are required only in trace quantities because they are not consumed in the reactions.

fat-soluble vitamin

one soluble in and absorbed from the intestine in fat. Includes vitamins A, D, E and K.

water-soluble vitamin

one soluble in water. Includes vitamins B and C.

Patient discussion about vitamin

Q. Should I take vitamins? I try to eat a healthy balanced diet everyday. Do I still need to take vitamins additionally?

A. Unless your Doctor told you that you suffer from a vitamin deficiency, then eating a healthy balanced diet is enough in order to get all the necessary vitamins. Make sure to eat fresh fruits and vegetables, which are rich with them. Also People who eat a vegetarian diet may need to take a vitamin B12 supplement.

Q. Are Vitamins really helpful? I realize that there's an entire industry around it but I was wondering how helpful vitamins really are.
Is there a difference between vitamins from fruits and vegetables and vitamins that you buy off the shelve?
Is there such a thing as taking too much vitamins?

A. Yes, vitamins are helpful. I recently stopped taking my supplement to see if I felt a difference. Once I stopped taking it my anxiety attacks returned and my energy level went down. Nutrition that we get from food is the best, but the truth is that we don't get the amount of nutrition that we need daily. Yes, it is a such thing as taking too many vitamins. This is why it is still good consult with your doctor when taking any kind of vitamin or supplement. When chosing a vitamin for myself price is not a concern when it comes to health. This is why I prefer more expensive vitamins rather than over the counter.

Q. what vitamins are recommended for treating cold? and what is the right amount of it ?

A. Actually, although studied in trials, vitamins C, E and zinc wasn't found to have a substantial effect either preventing or relieving the symptoms of common cold, so currently these vitamins can't be recommended for the treatment of common cold.

You may read more here: http://www.nlm.nih.gov/medlineplus/commoncold.html

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